Who’s suffering from City Hall’s biggest delusion: Mike Bloomberg or John Liu?

Bloomberg, for insisting that the winning bidder on the lucrative Tavern on the Green franchise did “exactly the right thing” by not disclosing he’s the brother-in-law of one of Mayor Mike’s top confidants?

Or Liu — for thinking for a moment that he has the moral standing to investigate the situation?

According to Bloomberg, the Emerald Green Group — co-owned by former Deputy Mayor Kevin Sheekey’s brother-in-law, Jim Caiola — shouldn’t have told officials about the family relationship.

Had he done so, the mayor piously insisted, “you would be asking me why they tried to get special treatment by name-dropping.”

Nice try, Mike.

The Philadelphia-based group beat out three local competitors for the right to run a restaurant on the Central Park site of Tavern on the Green over the next 20 years — a contract potentially worth millions.

City officials insist Caiola — whose sister is Sheekey’s wife, Robin — won the bid “on the merits, and the entire procedure was handled by the book.”

Maybe so, but no one should take City Hall’s word for it. After all, as former city Parks Commissioner Henry Stern noted: “This isn’t some hot-dog stand on Delancey Street that the guy is getting a deal on.

“Any relationship — blood, marriage, family — between the concessionaire and the city should be disclosed.”

Especially given Kevin Sheekey’s relationship with the mayor: He’s been Bloomberg’s political guru, was the cheerleader-in-chief and key strategist for his flirtations with a presidential run and is now a top exec at Bloomberg LP.

Speaking of cheerleaders, Mrs. Sheekey is a director of the politically freighted, leftward-leaning Center for Science in the Public Interest — the most vocal supporter of Bloomberg’s nanny-state diktats, like his ban on sugar-laden drinks.

Undue influence?

Probably worth a closer look.

But John Liu? (Insert horse-laugh here!)

The ethics-deficient comptroller has issues of his own with which to deal — and they’re a lot more serious than possible favoritism in awarding a city contract.

Indeed, they’ve already led to criminal charges.

Fact is, Liu is hardly qualified to recognize any ethical problem — even one staring him right in the face.

So he should leave the investigating to someone else and clean up his own house.

Actually, if ever a conflict of interest spoke for itself, it’s this one.